Article by Joanne M. Bargman, MD, FRCPC
Professor of Medicine, University of Toronto

Automated peritoneal dialysis (APD): PD with a cycler

APD has grown each year since it began in the 1980s, in part because it lets you adapt your treatment to your life. With days free, you can keep a job, care for children, do chores, or stay active in other ways. PD has fewer diet and fluid limits than standard in-center hemodialysis (HD). Other APD strengths include:

• Exchanges done while you lie down put less stress on your belly. You may be able to use more fluid, which cleans your system more.
• If you are a “fast transporter” (a test shows that your peritoneum has lots of pores and lets wastes through quickly), APD is a good choice. You can do exchanges with shorter dwell times so you don’t absorb the PD fluid.
• For people in nursing homes, APD is more convenient than doing 4 exchanges each day.

Your PD prescription: Volume

Case study: Mr. L

As head of a large real estate company, Mr. L (age 81) had a lot at stake when his kidneys failed. He trained for APD and did not need a daytime exchange because he had some kidney function left. Now, he has hired a personal trainer, walks 5 km a day, and still works part time.

To tailor APD, your doctor can change:

1. Your volume of PD fluid
2. Your dwell time
3. Your number of exchanges

With manual PD, the volume of PD fluid tends to match the bag size: 500 mL (about a pint), 1000 mL (about a quart), 2000 mL, 2500 mL, or 3000 mL. This means a fluid volume change for manual PD will always be 500 mL+.

With APD, the cycler can be very precise, and you can use just part of a bag. Changes in PD fluid volume can be as small as just 100 mL (about a third of a soda can). Over time, if you have some kidney function, it may decline. If that happens, your doctor can prescribe a little more PD at a time.

The difference is night & day

When you do APD, your doctor can prescribe a different fill volume at night, when you lie flat, than during the day, when you are upright. You can get more PD without feeling “stretched”.

Getting more PD without raising your intra-abdominal pressure can help if you have problems with leak of dialysis fluid or with hernias. Using a larger fill volume at night (and dry days) may also help your tissues heal after hernia repair surgery.

Your PD prescription: Dwell

Dwell time in PD is how long the PD fluid stays in your belly so wastes and water can flow into it.¹ With manual PD, dwells may be 8 hours while you sleep. Shorter dwells overnight are the norm with APD—but daytime dwells can be long (you might have a 15 hour dwell, or two 7.5 hour dwells).

Case study: Mrs. H

A small (48 kilo, 106 lb) Asian woman, Mrs. H could not handle 2 liters of PD fluid during the day. The answer? Now she does three 2-liter fills with APD at night over 9 hours, with a 1-liter last fill so she can do housework in the mornings. At mid-day, she does a 1.5-liter manual exchange.

Dialysis works by creating a gradient, or difference, in the level of wastes in the PD fluid vs. your blood.

If you are a “slow transporter” (your peritoneum has fewer pores, and lets wastes through slowly), reverse APD may work for you. Instead of doing a few fast exchanges at night, your doctor might prescribe two 4 or 4.5 hour exchanges plus two daytime exchanges spaced 7 or 8 hours apart.

As long as you make urine, you may not need a daytime exchange. If you need one but absorb fluid from it, some options to help are:

• Eating less salt
• Drinking less fluids
• Using a non-sugar based PD fluid (icodextrin)
• Using a stronger PD fluid (such as a 4.25% bag)
• Taking diuretics (water pills)
• Draining out the daytime fill at midday and staying dry or doing an exchange at that time

Your PD prescription: Number of exchanges

APD does not need to last longer than 8 or 9 hours or so at night. Rather than staying on a cycler for 10 to 12 hours tied to your bed, using the cycler for 6-9 hours and adding a mid-day exchange lets you have a full day off of the cycler.

Increasing the PD dose as kidney function falls

One option	Another option
Remaining kidney function is 10% or more APD Dose: 8 hours on cycler, 1.5 liters x 3 exchanges, last fill of 1 liter	Remaining kidney function is 10% or more APD Dose: 8 hours on cycler, 2 liters x 3 exchanges, day dry
No kidney function now APD dose: 9 hours on cycler, 2.2 liters x 4 exchanges, last fill of 1.5 liters, Mid-day exchange - 1.5 liters	No kidney function now APD dose: 9 hours on cycler, 2.5 liters x 4 exchanges, last fill of 2 liters - icodextrin

A “mid-day” exchange can be done on a work lunch break, in the afternoon (after school for a child), or even after supper—whenever it fits best into your day.

Often, APD is used to do many short exchanges during the night. But there are downsides to this practice:

• It is costly to use so much fluid.
• You need to store more boxes and lift more bags of PD fluid.
• “Middle molecules” like beta-2 microglobulin, which causes amyloidosis (a type of protein buildup that harms bones and joints) are not removed as well with short exchanges.
• If you are a “slow transporter” doing many short exchanges can impair your ability to remove salt from your body.

Using 3-4 cycler exchanges—and making them longer if needed—offers the best balance between good PD and lower cost.

Talk to your nephrologist

If you are tied to your bed doing APD for 10 or 12 hours or you absorb the daytime dwell and don’t feel your best, your doctor should be able to change your APD prescription to better fit your life.

The purpose of dialysis is not just to keep you alive—it’s to let you live fully and do things you enjoy. By tailoring the volume of PD fluid to your daily life and changing the dwell time and number of exchanges, your PD can make your life work better.

References

1. The PET Test for PD.

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